The ambient temperature sensor senses the temperature in the air surrounding the vehicle. and makes internal adjustments as necessary.  For example: If the outside temperature is 32 degrees, but you have your inside conditioning temperature set to 65 degrees, that 65 degree temp will seem a bit warmer than if you had it tuned to 65 degrees and it was 90 degrees outside.

It's almost as if your vehicle compensated to what it "thinks" the internal air should feel like considering the actual temperature outside.

The coolant temperature sensor is used to measure and track the temperature of the coolant in a vehicle. It can also prevent your vehicle from using less gas when this sensor is performing at optimal levels. This sensor is usually found near the engine thermostat.